Hydrocarbons obtained from subsurface formations are often used as energy resources, as feedstocks, and as consumer products. Concerns over depletion of available hydrocarbon resources have led to development of processes for more efficient recovery, processing, and/or use of available hydrocarbon resources.
In conventional processes, fluids obtained from a subsurface hydrocarbon formation may include water and gases and/or liquids. If the fluids obtained from a hydrocarbon subsurface formation contain a mixture of gases and liquids, the gases may be separated from the liquids. In instances where hydrocarbon gases are predominately produced from the subsurface formation, the hydrocarbon gases may be processed to remove impurities and/or inert gases to make fuel (for example, natural gas (pipeline gas), compressed natural gas (CNG), or liquefied natural gas (LNG)). Conventional processing of the subsurface formation gases may include treatment with a regenerative chemical extraction system such as an amine extraction system to capture hydrogen sulfide and/or carbon dioxide from the subsurface formation gases and produce a hydrocarbon gas stream. The hydrocarbon gas stream may be further processed to produce natural gas, CNG, or LNG.
Most commonly, hydrogen sulfide captured from subsurface formation gases is converted to elemental sulfur using a Claus process. The Claus process may be represented by the following equation: 2H2S+O2→2S+2H2O. Using the Claus process to treat hydrogen sulfide captured from subsurface formation gases that contain a significant amount of hydrogen sulfide produces a significant amount of elemental sulfur. The potential uses for the generated sulfur, however, have become limited due to oversupply and/or conversion of hydrogen sulfide to the elemental sulfur may be economically disadvantageous. The Claus process generates some power, however, the amount of power generated may be insufficient to operate the processing systems used to capture hydrogen sulfide from the subsurface formation gases and to produce natural gas, CNG, or LNG from the resulting hydrocarbon gas stream; thus supplemental power is required from other sources. A portion of the natural gas produced by the process and/or another fuel source are commonly used as fuel for generation of the required supplemental power.
Some sources of supplemental power are obtained by combusting a sulfur treatment process tail gas containing small amounts of sulfur compounds. For example, U.S. Pat. No. 5,092,121 to Ahner et al. describes a process for generating electricity by combusting a combustion fuel containing sulfur in a gas turbine. A sulfur treatment process tail gas containing carbon dioxide and sulfur-containing compounds is combusted in combination with a purified fuel gas stream in the combustor of a gas turbine or a supplemental firing unit to combust the sulfur-containing compounds. While more energetically efficient than the Claus process in the production of electrical power, the process is still relatively inefficient, and burning of the fuel may result in emission of carbon dioxide and sulfur dioxide to the environment.
Other methods for treating hydrocarbon gas streams containing hydrogen sulfide and/or carbon dioxide separate the hydrogen sulfide and/or carbon dioxide from the hydrocarbon gas stream and inject the hydrogen sulfide and/or carbon dioxide into a subsurface formation. These methods require power for separation, compression, and pumping of the hydrogen sulfide and carbon dioxide into the subsurface formation. The fuel for generating the power is generally supplied by burning a portion of the natural gas produced from the hydrocarbon gas stream and/or other fuel sources. Burning of the fuel is inefficient and may result in emission of carbon dioxide to the environment.
As outlined above, methods for treating hydrocarbon gas streams that contain hydrogen sulfide are known, however, hydrocarbon gas streams having greater than 2% by volume hydrogen sulfide are not generally chosen for development due to numerous concerns including corrosion, environmental emissions management, energy requirements for processing, and/or large amounts of elemental sulfur produced from associated Claus processes. As such, efficient, cost effective methods for processing streams containing hydrocarbons and significant quantities of hydrogen sulfide and/or combinations of hydrogen sulfide and carbon dioxide are desirable.